Engraving



Nov. 7, -11-333. J w, DALjoN 1,933,792

' ENGRAVING Filed July 19. 1932' 5 sheets-shed 1 Nov. 7, 1933. I J. w.DALTON 1,933,792

- ENGRAVING Filed July 19. 1932 5 Sheets-Sheet 2 NOV. 7,

- J. w. DALTON 1,933,792

ENGRAVING E'iledJuly 19. 1932 5 Sheets-Sheet s 1933- J. W.DALTON 1,933,79:- ENGRAVING Filed July 19, 1952 5 Shasta-Sheet 4 unnu'ntnnuuPatentedNov. 7, 1933 UNITED STATES ENGRAVING John Willey Dalton,Wimbledon, London, England, assignor to Daily Mirror Newspapers,Limited, London, England Application July 19, 1932, Serial No. 623,425,and in Great Britain June 9, 1931 screams. got. 173-5 This inventionrelates to the production of engraved surfaces with the aid of amechanical cutter, such as a drill, the operation of which iselectricallycontrolled as to its depth or width of cut in accordancewith the depth of tone of an. original through the intermediary ofmeans, for instance, an electro-magnet, adapted to impart a feedingmotion to the cutter, proportionate with the tone of that part of thesubject being scanned.

In the production of engraved surfaces in this manner the means inquestion has heretofore been of a character adapted to operate in suchmanner that within the limits of its working range the cutter may cutinto the surface to be engraved to any distance, according to the toneof light reflected from or transmitted through or by successive smallareas of a subject of which an engraved reproduction is desired in thesystematic scanning thereof with the aid of a light sensitive celladapted to control the operation of the electro-magnet.

The object of the invention is to provide an improved process andapparatus for the production of engraved surfaces in the manner firstabove specified, and more particularly to adapt such process andapparatus for the production of engraved surfaces for use in printingproc esses, as, for instance, in substitution for photomechanicallyproduced surfaces or blocks, or in the treatment of such surfaces orblocks for the purpose of underlaying, which is a measure resorted'tofor the purpose of increasing the corn trast in prints produced withtheir aid by reducing the thickness of the plate on which the surface isformed, and thereafter subjecting the plateto pressure while supportedon a resilient or elastic bed.

According to the invention the means for varying the feed of the cutteris of a character adapt ed to advance the cutter into the plate or thelike, the surface of which is to be engraved through one of a pluralityof distances or steps, prede termined as to number and relativemagnitude, each corresponding with a given tone or range of tones.

As will be understood, in undercutting the drill or other cutting toolwill be controlled as to its depth or width of cut in accordance withthe character of the corresponding portions of the printing surface ofthe plate.

To secure electrical control of the mechanical device there may beemployed any convenient means which is influenced in accordance with thedepth of tone of the original, for instance, a light sensitive cell, oralternatively the electrical control may be secured by local variationsin electrical resistance of the original or by capacity effects betweenan electrode and successive small areas of the original.

The cutter may be arranged to be fed through one of any number ofpredetermined distances, for instance, five different distancescorrespond ing with five different tones or a greater or less number oftones in accordance with the number of gradations of tone of which it isthought desirable to obtain a reproduction.

Thus, for example, in a hollow spindle adapted to be rotated, a cutterassociated with a means adapted to retain the point of the drillnormally out of contact with the plate or like member bearing thesurface to be engraved may he slid-- ably mounted and with the drill maybe associated a rod arranged co-axially with the drill and furnishedwith a plurality of armatures with which a corresponding number ofelectro-magnets are arranged to co-operate in such manner that accordingto which of the individual magnets is energized the cutter will be fedvarying distances into the member to be engraved.

For appropriately limiting. the several distances through which thecutter is fed by the action of the several magnets, stops co-operatingwith the armatures may be provided. For instance, the rod with which, aswell as with the drill, a spring may be associated in order to raise itinto its normal position of rest, may be provided with a piurality ofcollars, a corresponding number or" armatures being slidably mountedupon the spindle, the armatures and magnets being optionally so arrangedthat they (so-operate to form stops for regulating the distance throughwhich the rod will be moved consequent upon the energizing of therespective magnets.

The magnets may, with this construction, be mounted so that their axialposition relatively to one another and to the collars may be adjusted.

Thus, for instance, the magnets which may be formed of a plurality oflaminations arranged together to form radially extending U-shapedmembers, each set of U -shaped members forming or comprising two polepieces adjacent to the armatures, the winding being disposed between thehorns of the magnets, may be supported on plates conveniently of annularform provided with perforations adjacent to their periphery, theperforations in the several plates being arranged in register,screw-threaded rods passing through these perforations and associatedwith nuts, being provided for securing the plates in the desiredrelative positions.

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Normally, the drill will be arranged vertically within, and connected,for instance, by a dog clutch or the like with, the hollow armaturespindle of an electric motor secured to a bracket on a frame on which ismounted the magnets, the motor and its associated elements being mountedin such manner that they will be moved progressively with respect to thesurface to be engraved and. in accordance with the motion imparted tothe means for scanning the original subject or, alternatively, thesupply of electrical energy to the magnets may be controlled by theemployment of a light sensitive cell or light sensitive cells subjectedto the influence of light reflected from or transmitted by or throughthe subject.

For instance, a light sensitive cell subjected to the action of thelight reflected from or transmitted by or through successive small areasoi. the subject may be associated with any suitable means wherebyaccording to the amount of light influencing the cell, one or other orone or more of the magnets areenergized. I

The current flowing through the cells may, after suitable amplification,be used for energizing the magnets or, alternatively, the currentflowing through the cell may be arranged to operate one or other or oneor more .of a plurality of relays adapted to control the flow of currentthrough secondary circuits in which the windings of the magnet arearranged.

At this point may be mentioned that while in several instances referencehas been made to controlling the feed of the drill in accordance withthe tones of the successive small areas of the subject, the feed of thedrill may vary directly or inversely with respect to the tone of thesubject.

If, for instance, a printing surface of the character of a half-toneblock is to be produced, as will be understood, the feed of the drillwill increase in accordance with the lightness of the tone of thereproduction which is to be formed by the block. On the other hand, inthe production of an intaglio printing surface the greater the feedimparted to the drill the deeper will be the tone produced by theprinting surface.

The invention will be described further in detail with reference to theaccompanying drawings, in which:-

Figure 1 is a sectional elevation of the mechanical cutting deviceshowing the electro-magnets whereby the feed of the cutting tool iscontrolled;

Figure 2 is a diagrammatic representation of the cutting device asillustrated in Figure 1 in association with scanning means comprising alight sensitive cell with which is associated a suitable triode valveamplifier, the scanning means being arranged to operate upon an originalmounted upon a cylinder while the cutting tool is designed to operateupon another cylinder both secured on a shaft formed as a lead screw anddriven by a motor;

Figure 3 is a diagrammatic representation of an alternative arrangementin which a light sensitive cell is employed as a scanning means, thecutting tool being, in this case, arranged to operate upon a flat plate;

Figure 4 shows another arrangement of apparatus employing a lightsensitive cell as a scanning means, this arrangement being moreparticularly adapted for use in underlaying;

Figure 5 shows a further arrangement adapted for use more particularlyfor underlaying, the control of the cutting tool being secured bycapacity effect.

In the drawings, referring particularly to Fig ure 1, 1 is a guide inwhich is arranged the mounting 2, the lower end of which is providedwith a convex portion 3 adapted to rest upon the surface of the plate 4.

Within the mounting there are arranged a plurality of electro-magnets,of which the pole pieces are indicated by the reference 5. The polepieces are provided with extensions 6 passing through slots 7 in themounting and associated with rings 8 and 9 constituting nuts whereby theaxial position of the magnets with respect to the casing may beadjusted.

With the pole pieces there are arranged two windings 10, which will bereferred to as restraining windings formed in two sections connectedtogether in series and, further, with each magnet there are providedwindings 11, which will be referred to as operating windings each formedin two sections connected together in series. In addition, with .each ofthe magnets there is provided a field of winding 12 associated with thearmatures 13 which encircle a spindle 14 on which are provided aplurality of collars 15, 15a and 15b. The clearances between the severalcollars and their associated armatures varies as will be seen from thedrawings from a maximum in the lowermost magnet to a minimum in theuppermost magnet so that the movement imparted to the differentarmatures when their respective magnets are energized will cause thespindle 14 to be moved axially and in a downward direction throughvarying distances.

Thus it will be seen that if the lowermost magnet is actuated, the drillwill be caused to penetrate into the surface for a relatively shortdistance while if the middle magnet is actuated, the drill willpenetrate more deeply and if the uppermost magnet is actuated, stilldeeper penetration will take place.

In Figure 1, as will be seen, only three armatures are shown. Anyconvenient number of armatures and corresponding number of magnets maybe provided.

The axial movement of the spindle 14, which is occupied at its lower endin the collar 16 will feed the cutter 17 in a downward direction throughvarying degrees, the lower end of the spindle hearing upon the end ofthe cutter through the intermediary of the belt 18. The cutter isengaged in a collar 19 rotatably mounted in a bearing 20 provided in thecasing and formed to provide a pulley 21 engaged by a band '22 providinga driving connection with an electric motor or the like.

The other vend of the collar 19 is screwthreaded and there is engaged inengagement with it the .cap. 23 which has for instance a D-shaped slotengaging the forward edge of the cutter in such manner that by rotationof the collar 19, the cutter will be rotated and within the cap there isarranged a spring 24, one end of which bears upon the lower end of thecap and the other upon the washer 25 engaged about the cutter andoperating to move the cutter in the opposite direction from that inwhich it is urged by the energizing of the several magnets.

In the construction shown in Figure 2, A represents the cutting deviceas a whole substantially as shown in Figure 1, 12 indicating the fieldwhich is formed the lead screw 29 and on cylinders 30 and 31 at theopposite ends thereof are arranged, respectively, the original of whichthe engraved reproduction is to be formed and the plate to be engraved.

On the end of the motor shaft there is provided a contact maker 32connected by the leads 33 with the operating windings 11 and throughthem by way of the lead 34, 34a, 34b, 34c, 3411 with the anodes 35, 35a,35b, 35c, 35d of the valves 36, 36a, 36b, 36c, 36d, the filament heatingleads of which are indicated by the reference 37, a potentiometer 38being arranged between these leads and connected with the lead 39 with.the source of anode voltage 40.

Grids 41, 41a, 41b, 41c, 41d are connected through the resistances 42,42a, 42b, 42c, 42d with tapping points on the resistance 43 connected atone end to the grid bias battery 44, the positive'of which is connectedwith the negative of the source of anode voltage, the common point beingconnected through the lead 45 with the restraining windings 10. Theopposite ends of the resistance 43 are connected through a rectifier 46and an amplifier 47 with the light sensitive cell 48 with which isassociated a reflector 49, the purpose of which is to reflect on to thelight sensitive cell the light projected from the source of illumination50 to the interrupter disc 51 mounted on the spindle of the electricmotor 52 and concentrated by the lens 53 to a pencil of rays projectedthrough the lens on to the original mounted upon the cylinder 30.Variations in the amount of light falling upon the cell will causevariation in the voltage supplied by way of the amplifier and rectifieracross the tapped resistance 43 thus causing one or other of the valves,which may be thermionic valves or mercury vapour valves, to beinfluenced and energize one or other of the windings 11.

The construction shown in Figure 3 operates generally in a similarmanner to the construction previously described but in this case thesurface to be engraved indicated by the reference 54 is mounted upon asupport 55 slidably arranged in a frame 56 and adapted to be movedrelatively to the frame through the intermediary of the bands 57engaging pulleys 58 secured to the frame and passing over pulleys 59 onthe spindle 60, the motor 61 operating to drive the pulleys 58 throughgearing of any suitable construction adapted to cause reversal of thedirection of movement of the support 55 at appropriate times.

Movement of the support and its associated frame in a direction at rightangles to the direction of movement imparted to it through the bands 57is secured by the motor 62 and the lead screw 63 on one end of which toprovide a sprocket 64 engaging a chain 65 in driving engagement with thesprocket 66. The mechanism in question is secured to a base board 67 towhich is connected a pantograph device 69 through which is impartedcorresponding motion to the support 70 slidably engaged in the frame '11in turn slidably mounted in the opening 72 in the base board, '73representing the original to be operated upon which, in this case is atransparency, '74 indicating a source of illumination associated with alens 75 adapted to concentrate a pencil of rays upon the original, aspot of light formed on the original illuminating in turn the lightsensitive cell 76 which is connected with a rectifier 77, the output ofwhich is connected, as in the case of the construction shown in Figure2, across the resistance 43. This resistance and its associatedresistances v3 and valves are connected up generally in the same manneras in the previous construction and hence similar references are used todenote equivalent parts. In this construction, however, a source ofsupplyof alternating current 78 is provided instead of a source ofcontinuous current, one lead '79 thereof being connected to thegrid'bias battery 44 and to the slider of the potentiometer 38.

.The other lead 80 is connected with the electromagnets of a cutteroperating in a similar manner to the cutter previously described.However, in this case the details of construction are slightlydifferent. 81 are the magnets, 82 being the armatures, 83 the collarsprovided on the spindle 84, 85 being a spring adapted to move the cutterin a reverse direction from that in which it is urged by the energizingof the magnets. Y 1

In this construction condensers 86 are shown across the leads connectedwith. the magnets, the

provision of similar condensers being desirable also in the case of theconstruction described in the preceding figure.

The construction illustrated in Figure 4 is an arrangement designedforcontinuous or stepwise operation with scanning by interrupted lightreflected from the engraved original, the drilling being arranged tooperate upon the opposite surface of the original as in underlayingphoto-mechanically produced blocks.

The cutter, which is again represented by the reference A, is of theconstruction shown in Figure 1, 12 indicating the field windings, 11 theoperating and 10 the restraining windings. Across these windings arearranged condensers 86 and 87. The restraining windings are connectedthrough the variable resistances 88, 88a, 8822, through the lead 89 tothe negative 90 of the source of direct current supply and the operatingwindings are connected with the plates 91, 91a, 91b of-the mercuryvapour valves or thyratron tubes 92, 92a, 92b, the filaments of whichare heated by current supplied thereto by way of the leads 93 fromthe'secondary 94 of a transformer, the primary of which is indicated bythe reference 95.

The grids of the valves are connected by leads 96, 96a, 961) through theresistances 97, 97a, 97b with tapping points on the resistance 98 in theplate circuit of a thermionic valve 99 designed to function as a leakygrid detector, this valve-being as shown, of the indirectly heatedcathode type,

heating current being supplied by way of the leads 100 from thesecondary 101 of the transformer, the primary of which is indicated bythe reference 95. 102 indicates the grid leak associated with this valveand 103 the grid condenser.

104 is the inter-valve transformer coupling the valve with a secondvalve 105 also of the indirectly heated cathode type which, in turn, isconnected with a similar valve 106, the heating current being suppliedto these valves by way of the leads 107 from the secondary 108 of thetransformer of which the primary is indicated by the reference 95.

The cathodes of these two valves are connected through grid biasresistances 109 and 110 shunted by condensers 111 and 112 by the lead113 to earth, 114 and 115 indicating the grid leaks and 116 and 117coupling condensers, 118, 119 being anode resistances connected, as alsois the resistance 98, with the positive lead 120 from the anode battery121, the negative pole of which is connected to earth.

The condenser 122 is arranged in the lead from the grid of the valve 106and the lead 123 which is connected through the" resistance 124 toearth. The lead 123 extends to the light sensitive cell 125, the otherlead from which 126 is connected with the light sensitive cell biassingbattery 127. The photo-electric cell is arranged in association with amirror 128 which operates to reflect on to the cell the light which isin turn reflected on to it from the surface of the original 129 which isilluminated by the pencil of rays 130 from the source of light 131concentrated by the lens 132.

In the path of the light from the source of illumination 131 there isarranged an interrupter disc 133 driven by a motor 134. The original ismoved with respect to the pencil of rays projected on to it through thelens 132, in a stepwise or continuous manner as in the operation ofscanning and the varying illumination of the cell supplies a varyinginput to the valve 106, the output of which, after amplification, issupplied to the valve 99 functioning as a leaky grid detector. Rectifiedcurrent passing through the detector will operate to permit current toflow through one or other of the thyratron tubes 92, 92a, 92b. Theproperty of these tubes is that once having been activated by raisingtheir grid voltage to a particular value they will continue to allowcurrent to pass and consequently it is necessary to provide means forinterrupting the passage of current and this is effected by interruptingthe anode voltage applied to them. The interruption of the anode voltagein this construction is effected with the aid of the valve 135 to whichfilament current is supplied by the leads 136 from the secondary 137 ofthe transformer, the primary of which is indicated by the reference 95.

In circuit with the grid biassing battery 138 of this valve is arrangedan alternator 139 and the anode 140 of the valve is connected throughthe lead 141 with a centre tapped inductance 142 the centre tapping ofwhich is connected by the lead 143 with the source of direct currentsupply of which the negative is indicated by the reference 90, one ofthe outer ends of the inductance being connected with the field windings12 of the cutter. Across this inductance is arranged a condenser 144 andby this means there is supplied to the thyratron tubes at intervalscurrent adapted to interrupt the operation of the tubes.

In the construction illustrated in Figure 5, control of the cutting toolis effected by a capacity effect which, assuming that a scanning memberof a given area and functioning as an electrode is moved relatively tothe engraved surface a layer of a di-electric extending between theelectrode and the engraved surface, will vary in accordance with thevariation in the effective area of the engraved surface adjacent to theelectrode. For instance, assuming that the engraved surface is of thetype produced by the half-tone process, the total area of the faces ofthe elevation on any given area of the surface will vary in accordancewith the tone of the impression which will be produced by the aid ofsuch variation of the surface consequently when the electrode is overaportion of the surface which will give a dark impression the capacitywill be greater than if the surface were of the character to give alighter impression.

weaves spaced relationship with the engraved plate 145 so as to securebetween it andthe engraved plate a condenser effect. The plate 146 isconnected by the lead 147 with an inductance 148 connected with a gridof the valve 149 which as shown is of the indirectly heated type, thegrid being connected also by the resistance 150 with the lead 151connected with the negative terminal of the source of supply ofdirect-current. To the same negative lead is also connected through theinductance 152 shunted by the condenser 153 the grid of the valve 154 inthe plate circuit of which is arranged an inductance 155 loose coupledwith the inductance 152 and also the inductance 156 which is loosecoupled to the inductance 148. The valve 154 is also, as will be seen,of the indirectly heated type and its cathode is connected through theresistance 157. with the negative lead in question, a by-pass condenser157a. being arranged in shunt with the resistance.

Similarly, a resistance 158 and condenser 159 are associated with theindirectly heated cathode of the valve 149. In addition, the grid of thevalve 150 which is coupled through the condenser 161 with the'anode ofthe valve 149 is connected through the resistance 162 and condenser 163with the negative lead 151 and to the negative lead is also connectedthe grid bias battery 164 and the potentiometer resistance 165, theslider 166 of which is connected with the lead in which the resistance162 is located. The cathode of this valve is connected by the lead 167with the negative lead in question while the plate of the valve isconnected through the condenser 168 with the negative and in addition itis connected through the choke 169 with one end of the resistance 170with which a plurality of tapping points are connected throughresistances 171, 171a and 171?), these resistances being in turnconnected respectively with the grids of the valves 172, 172a and 1722).These valves may be thermionic or mercury vapour valves (thyratron) andthe filament current is supplied thereto by the secondary 173 of. atransformer, the primary 174 of which is connected with a source ofalternating current supply. Further, with this source of alternatingcurrent is connected the primary 175 of a transformer the secondary 176of which is provided with a centre tapping 177 connected with one end ofthe resistance 170, one end of the secondary winding being connected bythe lead 178 with the field windings of the electro-magnets of thecutter which, in the construction described in Figure 5 is provided withby-pass condensers. The restraining windings of these magnets areconnected through the variable resistances 179, 179a, 1792), 1790,17911, with, respectively, rectifiers 180, 180a, 180b, which may be ofthe valve type or metallic rectifiers with the lead 181 connected withthe other end of the transformer winding 176 and also by ,way of thelead 182 with earth and a common negative lead 151.

The operating windings 11 of the cutter are connected by the leads 183,183a, 183b, respectively with the plates of the valves 172, 172a, 172band, as will be seen, the earth lead 182 is connected by the lead 184with the engraved plate 145.

As the engraved plate is moved with respect to the electrode 146, thecapacity in the grid circuit of the valve 149 will be varied and thefrequency of the oscillations set up therein by the oscillator valve 154will likewise be varied and the oscillating current thus set up will,after rec- Leeaea tiflcation by the valve 149, be amplified by the valve160 and applied across the resistance 1'70 and according to themagnitude of the current, one or other of the valves 172, 172a, 172b,will be actuated with the result that corresponding electromagnetswill'be energized and the feed of the cutter into the rear face of theengraved plate 145 will be varied.

With this arrangement, aswill be seen, the alternating current issupplied to the valves 1'72, 172a, 17212 so that if they are of themercury vapour type, the passage of current therethrough will beinterrupted at a frequency corresponding with the periodicity of thealternating current supplied from the source of alternating current tofeed the primary 174, 175 of the transformers.

In conclusion, it is to be pointed out that the above description isfurnished for the purpose of explaining the nature of the invention andvarious changes may be made in the details of construction andarrangement above referred to without exceeding the scope of the presentapplication.

Having now described my invention what I claim as new and desire tosecure by Letters Patent is:

1. Apparatus for producing on a suitable surface an engravedreproduction of an original subject comprising a cutter, a plurality ofelectromagnets associated with the cutter, and means magneticallyassociated with the electromagnets and mechanically associated with thecutter adapted, according to which of the individual electromagnets isenergized, to advance the cutter into the surface to be engraved throughone of a plurality of distances predetermined as to number and relativemagnitude.

2. Apparatus for producing on a suitable surface an engravedreproduction of an original subject comprising a cutter, a plurality ofelectromagnets, armatures mechanically associated with the cutterco-operating with the electromagnets and adapted according to which ofthe individual magnets is energized to advance the cutter into thesurface to be engraved through one of a plurality of distances,predetermined as to numher and relative magnitude.

3. Apparatus for producing on a suitable surface an engravedreproduction or an originalsubject comprising a cutter, a plurality ofelectro tromagnets, armatures mechanically associated magnets, armaturesmechanically associated with the cutter co-operating with theelectromagnets and adapted. according to which of the individual magnetsis energized to advance the cut ter into the surface to be engraved.through one of a plurality of distances, predetermined as to number andrelative magnitude, and stops cooperating with the armatures adaptedappropriately to limit the several distances through which the cutter isfed by the action of the several magnets.

4. Apparatus for producing on a suitable surface an engravedreproduction-of an original subject comprising a cutter, a plurality ofelecwith the cutter co-operating with the electromagnets and adaptedaccording to which of the individual magnets is energized to advance thecutter into the surface to be engraved through one of a plurality ofdistances, predetermined as to number and relation magnitude,stops-co-operating with the armatures adapted appropriately to limit theseveral distances through which thecutter is fed by the action of theseveral magnets, and means adapted to permit adjustment in an axialdirection of the magnets relative to one another and to the stops.

5. Apparatus for producing on a suitable surface an engravedreproduction of an original subject comprising a hollow spindle, acutter slidably mounted within the spindle, means adapted to retain thepoint of the cutter normally out of contact with the surface to beengraved, a plurality of electromagnetsassociated with the cutter, eachconsisting of a plurality of laminations arranged together to formradially extending U-shaped members so as to form two pole pieces,windings disposed between the pole pieces and means for adjusting theseveral magnets relative to one another and to the spindle, a rod withinthe hollow spindle arranged co-axially with the cutter, armaturesassociated with the rod and located adjacent to the pole pieces of theelectromagnets adapted according to which of the individual magnets isenergized to advance the cutter intothe surface to be engraved throughone of a plurality of distances predetermined as to number and relativemagnitude.

JOHN WILLEY DALTON.

